DE-B-1 250 026 discloses a heating cable, in which pieces of electrical resistance conductors are soldered or welded to pieces of copper conductors so as to produce a continuous length of a heating cable conductor. The continuous length is provided with a continuous insulating layer and other protective layers and sheaths.
The continuous length is cut into predetermined sections of heating cables with “cold ends” that is that a piece of an electrical resistance conductor has two ends of copper conductors. The purpose of the cold ends is that when the heating cable is installed the terminations and interconnections of the heating cables are displaced from the heating areas. Another purpose is that quite often the heating cable route leading from the switch or termination on a wall to the heated floor will pass over or through building sections which should not be heated.
Single conductor heating cables have some essential drawbacks. Both ends of the heating cable must be connected to the house wiring system. This procedure is very time consuming.
Single conductor heating cables generate electromagnetic fields (EMF). The EMF discussion now and then pops up due to environmental/health considerations/awarenees.
EP-A-0 858 244 discloses a heating cable which reduces the generation of electromagnetic fields. The cable consists of a central resistance conductor, a concentric sheath of insulation material surrounding the resistance conductor and return conductor means arranged to be interconnected with the resistance conductor in the far end of the cables. The return conductor means consists of at least two separate conductors which are distributed in the cable core. The return conductors are preferably embedded in a common insulation sheath arranged over the resistance conductor sheath. The production of such a heating cable is very cost intensive.